1. Field of the Invention
The present invention relates to a microscope having a confocal point and a non-confocal point, and a confocal point detect method applied thereto.
2. Description of the Related Art
Conventionally, a laser microscope has been known of scanning type which scans a sample with a laser beam and forms an image of the sample in accordance with the scanning. In this kind of scanning type laser microscope, transmitted or reflected light from a sample being scanned is converted into a photoelectric signal by means of a photoelectric converter such as a photomultiplier tube or a photodiode, and this photoelectrically converted signal is quantized by an A/D convert circuit. Thereafter, the converted signal is stored in a memory. Also, as a scanning type laser microscope of this kind, there has been a microscope with a focusing point adjust function for automatically adjusting a focusing point of an image. For example, as disclosed in Japanese Patent KOKOKU Publication No. 4-61334, a linear image sensor for forming a confocal image is used, and a focusing point detector is provided which receives a part of a light flex injected into the linear image sensor, to detect focusing point information. In accordance with an output signal from the focusing point detector, the distance between an objective lens and a sample is controlled with respect to a focusing point.
However, in such conventional microscopes, a part of a light flux injected into a linear image sensor for forming a confocal point image is injected into a focusing point detector, and therefore, the light amount of the light injected into the linear image sensor for forming a confocal point image is reduced, so that a sample image sometimes cannot be observed for a sample under slightly weak light conditions. In addition, in order to carry out a focusing point adjustment with high accuracy, the optical focusing point position must be optically adjusted between the linear image sensor for forming a confocal point image and the focusing point detector. If the position is not sufficiently adjusted, and therefore, complicated adjustment operations may be required, so that time and labor are wasted. Further, although focusing can be carried out by means of a confocal point image obtained by laser scanning, the focal depth of a confocal point image is so small. Therefore, a confocal point image is difficult to use, and there is a risk that the focusing point position cannot be determined, so that an objective lens may collide into a sample.
On the other hand, it is known that this kind of confocal scanning type optical microscope exhibits a sectioning effect in a confocal mode, and exhibits the same imaging characteristic as a conventional microscope in a non-confocal mods, as described in T. Wilson, "Theory and Practice of Scanning Optical Microscopy", ACADEMIC PRESS 1984, for example.
A conventional confocal point scanning type optical microscope is shown in Japanese Patent Application KOKAI Publication No. 61-219919. FIG. 1 is a view of an optical system, showing a first example of a conventional confocal point scanning type optical microscope. A light beam 50 from a laser light source (not shown) considered as a point light source is injected into a first optical deflector 52, passing through a beam splitter 51.
This optical deflector 52 is provided at a position common to a pupil 54 of an objective lens 53.
When the optical deflector 52 does not perform deflection, the light beam 50 goes along a light axis 55. When the optical deflector 52 performs deflection, e.g., the light beam 50 is subjected to scanning, the direction of the light beam 50 corresponds to an off-axis main light beam 56 and the center of the light beam 50 corresponds to the off-axis main light beam 56, since the optical deflector 52 is provided at the position of the pupil.
Next, the light beam 50 passes through pupil projection lenses 57 and 58, and is injected into a second optical deflector 59 provided at the position of the pupil. If this optical deflector 59 performs scanning in the Y-direction among directions of two dimensional scanning, the optical deflector 52 performs scanning in the X-direction.
The light beam subjected to two-dimensional scanning by the optical deflectors 52 and 59 is injected into the pupil 54 of the objective lens 53 by the pupil projection lens 60 and an imaging lens 61. Further, the light beam creates point light limited by diffraction, on a sample 62 by the objective lens 53. By performing two-dimensional scanning in the X- and Y-directions by means of the optical deflectors 52 and 59, the sample 62 is subjected to two dimensional scanning by the point light.
The light beam reflected from the sample 62 passes through the objective lens 53 and the pupil 54, and further passes through the imaging lens 61, thereby forming an image. The imaging surface of this image is a surface where the image is observed by a conventional optical microscope. The light beam further is returned to an optical deflector 59 by the pupil projection lens 60.
Thus, a reflected beam passes through the same path through which the beam has been injected into the sample 62, in the reverse direction, and thus returns to the beam splitter 51, This beam is picked up by the beam splitter 51 and forms a detection beam 67. Since the reflected beam returns after having passed through the optical deflectors 59 and 52, the detection beam 67 is not shifted even if the off-axis light beam is subjected to scanning. The detection beam 67 is diaphragmed onto a point by a converging lens 66. If a pin hole 69 is provided at the position where the detection beam is diaphragmed and is detected by a detector 70 behind the position, it is possible to obtain an image with a higher resolution than a conventional microscope, which does not include flares. In this case, it the pin hole 69 is withdrawn at this position, it is possible to obtain a non-confocal point image.
Since the confocal point scanning type optical is microscope as described above has a sectioning effect, it is difficult to perform focusing. For this reason, a non-confocal point light path, an eye observation light path illuminated by a white light source, or a TV observation light path conventionally applied.
FIGS. 2 and 3 are views of the optical systems respective second and third examples of different conventional confocal point scanning type optical microscopes.
In FIG. 2, a mirror 71 is provided on a light path such that the mirror is movable in the forward and backward directions on a light path. The detection beam 67 reflected by inserting the mirror 71 into the light path is diaphragmed by a converging lens 72, and is detected by the detector 73, so that a non-confocal point image is obtained. In addition, the detection beam 67 is diaphragmed onto a point by the converging lens 68, by removing the mirror 71 from the light path, and is then detected by a detector through a pin hole 69, so that a confocal point image can be obtained. By thus moving forwards or backwards the mirror 71, a confocal point image and a non-confocal point image can be selected.
In FIG. 3, a mirror 74 Is provided on a light path between an imaging lens 61 and an objective lens 53, such that the mirror 74 is movable in the forward and backward directions. By inserting this mirror 74 into the light path, illumination light from a white light source 75 passes through an half-mirror 76 and an imaging lens 77, and is irradiated onto a sample 62, reflected by mirror 74. The observation light relating to the sample 62 is introduced to a TV camera 78, so that a conventional drop illumination image can be obtained. In addition, a confocal point image can be obtained in the same manner as in the second example, by removing the mirror 74 from the light path. According to the structure of FIGS. 2 and 3, a confocal point scanning type optical microscope can be provided which performs focusing by means of a non-focal point or a drop illumination image, to achieve focusing in the same manner as in conventional microscopic observation.
According to the conventional structures described above, a confocal point scanning type optical microscope is provided which simultaneously detects focusing points by means of both a confocal point image and a non-confocal point image.
However, in the confocal point scanning type optical microscope shown in FIGS. 2 and 3, the mirrors 71 and 74 must be mechanically moved forwards and backwards to switch light paths, and the switching operation requires a significant amount of time, so that the operation feels troublesome for observers.
In addition, the mirrors 71 and 74 must be provided with a mechanism for moving themselves forwards and backwards, and therefore, the price of the apparatus becomes high and the size thereof must be enlarged, particularly in the case where the switching operation is electrically performed.
The present invention has an object of providing a focal point detect method by which focusing point adjustment can be carried out with high accuracy and rapidity.
The present invention has another object of providing a microscope which is capable of simultaneously detecting a confocal point image and a non-confocal point image, and which is capable of performing immediate selection between a confocal point image and a non-confocal point image.